Power tube



Aug. 19, 1930.

'D. A. MULLANEY POWER TUBE Filed Sept. 14, 1925 Q m; n mn 0% .t bu M m 8. E h Q S D.

Patented Aug. 19, 1930 UNITED STATES PATENT OFFICE DUDLEY A. MULL ANEY, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELEC- TRIO COMPANY, A CORPORATION OF NEW YORK POWER TUBE Application filed September My present invention relates to power tubes of the pliotron type. In tubes of this type, the filament leads sometimes extend through metal to glass seals which are exposed to ion bombardment during both the evacuation and operation of the tubes. This bombardment tends to weaken the seals and thereby destroy the vacuum in the tube. It is one of the objects of my invention to provide an arrangement whereby such seals may be effectively shielded from ion bombardment.

It is a further object of my invention to provide improved means for supporting the filament and for spacing the grid and fila- 5 ment from the surrounding anode.

The novel features which I believe to be characteristic of my invention are set forth with particularity in the appended claims. My invention itself, however,-both as to its 2o organization and method of operation, will best be understood from reference to the following specification taken in connection with the accompanying drawing, in which Fig. 1 represents an elevation of the power tube, the outer portions thereof being indicated in dotted lines. Fig. 2 is a perspective view on an enlarged scale of the filament support and grid spacing means. Fig. 3 is a cross-sectional view taken along line 3-3 in Fig. 1.

- Referring to the drawing, I have indicated thereon, in dotted lines, an elongated con tainer including a glass member 1, a metal anode 2, and an intermediate metal sealing cone 3. Fused to the member 1 is a glass envelope 4, within which is located a reentrant glass tube 5, fused at one end to the envelope 4, and provided at the other end with a pair of branches 6 and 7 adapted to support a cathode 8. A pair of stiff conductors 9 and 10, which preferably consist of tungsten, extend through the branches and supply current to the filamentary cathode 8. A pair of metal thimbles 11 and 12,'which may consist of a copper plated, nickel-iron alloy, or other suitable metal, are fused to the conductors and to the glass branches. The tips of the branches are sealed over the thimbles, the

sealing operation being assisted by a coating of borax or other suitable flux;

.Mounted on conductors 9 and 10 is a pedes- 14, 1925. Serial No. 56,106.

tal 13 which may consist of tungsten or other refractory metal. .The pedestal is mounted on a clamp 14 consisting of small plates of refractory metal provided with interposed strips of mica or similar insulation and held together by wire fastening means as indicated at 15.

The glass envelope 4 extends somewhat beyond the metal thimbles 11 and 12. and the end of the envelope adjacent the thimbles is provided with a relatively small and inwardly directed flange 40. Mounted on the stiif conductors 9 and 10 between the inwardly directed flange and the metal thimbles is a pair of semicircular metal shields 16 and 17, having a radius equal approximately to the radius of the envelope 4 and overlapping slightly, as indicated in Fig. 1, to substantially close the end of the envelope. lVith this arrangement the metal to glass seals are substantially enclosed and completely shielded from ion bombardment in all directions.

The grid supporting structure-18 comprises a pair of metal collars 20 on which are supported a plurality of longitudinally extending wires 19. The grid or control element is in the form of a coiled wire 21 which is secured to the wires 19. The grid cage is supported on four stiff wires 22 which are permanently connected to a metallic collar 23, which surrounds the envelope 4 and is spaced therefrom by a fine copper wire mesh 24. An electromotive force may be supplied to the grid through a terminal 25.

Mounted on the lower end of the grid supporting structure. is a flat insulating quartz plate 26, provided with cut-away or grooved portions 27 adapted to accommodate certain of the longitudinally extending wires 19. Small metal plates 28 riveted to the ends of wires 19 serve to confine the plate 26 between them and'the lower grid collar 20. v

The insulating plate 26 is provided with oppositely extending coaxial quartz stems, one of which 29'is provided with a pair of coaxial grooves 30 and 31 adapted to accom modate metal bands 32 and 33, the bands being provided with hooks 34 and 35 adapted to receive the looped portions of the filamen tary cathode 8.

The cathode 8 is permanently connected to the ends of the stiff conductors 9 and 10 and carried over the hook members 34 and 35, as indicated in Fig. 2. The upper looped portion of the filament includes a still U-shaped member 36 soldered or otherwise perinanently connected to the pedestal 13 and permanently connected to the filament wires by means of a thin binder wire 37 and solder. The lower stem 38 of the insulating plate 26 is provided with a hollow bowl-shaped portion 39 shaped to have an external surface similar to the internal surface at the lower extremity of the anode, as indicated in Fig. 1.

With the particular insulator shown, the number of metal parts is reduced to a minimum and the grid may be guided within the anode by the extension 39 and always positively spaced therefrom. By the elimination of the usual central metallic support for the filament, I prevent short circuits of the filament thereon, and at the same time reduce the gassing of the tube caused by the presence of the metal.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electron discharge device comprising a tubular member having a plurality of branched portions, conductors extending through said tubular member and branched portions and connected to the branched portions, a hollow envelope connected to one end of the tubular member and extending beyond the point of connection of the conductors and branched portions, and shielding means cooperating with the envelope to substanti ally enclose said branched portions.

2. An electron discharge device comprising a tubular member having a plurality of branched portions, a metallic thimble connected to each of said branched portions, conductors connected to each of said thimbles, a hollow vitreous envelope connected to one end of the tubular member and extending slightly beyond said metallic thimbles, and shielding means mounted within the end of said envelope and adjacent the metallic thimbles.

3. An electron discharge device comprising a tubular member having a plurality of branched portions, a metallic thimble connected to each of said branched portions, condoctors connected to said thimbles, a hollow vitreous envelope connected to one end of the tubular member and extending slightly beyond said metallic thimbles, and shielding means on said conductors adjacent one end of the envelope.

4. An electron discharge device comprising a tubular member having a plurality of branched portions, a metallic thimble connected to each of said branches, conductors connected to each of said thimbles, a hollow vitreous envelope connected to one end of the tubular member and extending slightly beyond said metallic thimbles, and metallic discs mounted on said conductors between said thimbles and the end of the envelope adjacent thereto.

5. An electron discharge device comprising a filamentary cathode and a control element, supporting means for the control element, an insulator mounted on the supporting means, said insulator having a plurality of coaxial grooves and supporting means for the filament mounted in said grooves.

6. An electron discharge device comprising a filamentary cathode and a control element, supporting means for the control element, an insulator mounted on the supporting means, said insulator having a grooved extension adapted to accommodate means for supporting the filament.

7. An electron discharge device comprising an anode, a cathode and a control element concentrically arranged, an insulating plate mounted at one end of the control element, the plate having coaxial oppositely extending integral members, one of said members providing means to support the cathode, the other of said members being provided with means for spacing the control element from the anode.

8. In combination, an electron discharge device comprising an anode, a cathode, and a control element, an insulating plate mounted at one end of the control element, said insulator being provided with an integral stem, a hollow insulator member mounted at one end of said stem and integral therewith, the external surface of said member cooperating with the internal surface of the anode to space the control element therefrom.

9. An electron discharge device comprising an anode, a filamentary electrode and a control element, an insulator extending longitudinally of the discharge device, means for rigidly spacing the insulator from the control electrode, means for supporting the filamentary electrode from one end of the insulator, and means for spacing the opposite end of the insulator from the anode.

In witness whereof, I have hereunto set my hand this 11th day of September, 1925.

DUDLEY A. MULLANEY. 

